U.S. patent application number 10/923180 was filed with the patent office on 2006-02-23 for impact strength improvement of regrind.
Invention is credited to Allen T. Mika, Anthony Poloso.
Application Number | 20060040121 10/923180 |
Document ID | / |
Family ID | 34956320 |
Filed Date | 2006-02-23 |
United States Patent
Application |
20060040121 |
Kind Code |
A1 |
Poloso; Anthony ; et
al. |
February 23, 2006 |
Impact strength improvement of regrind
Abstract
Regrind is mixed with at least one low density metallocene
polyethylene to increase the amount of regrind that can be used in
a thermoformed article.
Inventors: |
Poloso; Anthony;
(Praireville, LA) ; Mika; Allen T.; (Baton Rouge,
LA) |
Correspondence
Address: |
ExxonMobil Chemical Company;Law Technology
P.O. Box 2149
Baytown
TX
77522-2149
US
|
Family ID: |
34956320 |
Appl. No.: |
10/923180 |
Filed: |
August 20, 2004 |
Current U.S.
Class: |
428/516 |
Current CPC
Class: |
C08L 2207/20 20130101;
Y10T 428/3175 20150401; Y10T 428/13 20150115; B32B 5/14 20130101;
B32B 2307/7242 20130101; B32B 2439/40 20130101; Y10T 428/31938
20150401; B32B 27/08 20130101; C08L 23/06 20130101; Y10T 428/31797
20150401; B32B 2307/308 20130101; Y10T 428/31913 20150401; C08L
2666/06 20130101; B32B 1/02 20130101; B32B 27/306 20130101; B32B
2250/24 20130101; Y10T 428/1352 20150115; B32B 2307/7265 20130101;
Y10T 428/31746 20150401; B32B 2270/00 20130101; B32B 2272/00
20130101; C08L 23/04 20130101; Y10T 428/31725 20150401; Y10S
264/917 20130101; Y10T 428/31739 20150401; Y10T 428/31757 20150401;
B32B 27/327 20130101; C08L 23/04 20130101; Y10T 428/31909 20150401;
Y10T 428/1359 20150115; B32B 2307/558 20130101; B32B 2605/08
20130101; B32B 27/34 20130101; C08L 2314/06 20130101; B32B 27/32
20130101; B32B 2250/244 20130101; Y10T 428/31743 20150401 |
Class at
Publication: |
428/516 |
International
Class: |
B32B 27/08 20060101
B32B027/08 |
Claims
1. An article comprising regrind and at least one material selected
from low density polyethylenes.
2. An article made by a process, said article comprising: (A) a
layer comprising polyethylene; (B) a layer comprising a material
incompatible with polyethylene; and (C) a layer comprising regrind
from said process, and at least one material selected from low
density metallocene polyethylenes, wherein said regrind contains
adhesive.
3. The article of claim 2 wherein said polyethylene is selected
form HDPE homopolymer, HDPE copolymer of ethylene and a C3-C12
alpha olefin, and mixtures thereof.
4. The article of claim 2 wherein said layer (A) comprises an alloy
or blend of polyethylene.
5. The article of claim 2 wherein said article further comprises at
least one adhesive tie layer.
6. The article of claim 2 wherein said polyethylene is an HDPE
having a density of from greater than about 0.940 g/cc to about
0.965 g/cc according to ASTM D-4883 and an HLMI of from about 3.0
to about 40.0 according to ASTM D-1238-65T, Condition F.
7. The article of claim 2 wherein said material incompatible with
polyethylene is a material comprising a resin selected from
ethylene vinyl alcohol copolymer, polyamide, polyketone, ethylene
vinyl acetate copolymer, polyester, and mixtures thereof.
8. The article of claim 2 wherein said material incompatible with
polyethylene is a material comprising a resin selected from
ethylene vinyl alcohol copolymer, polyamide, and mixtures
thereof.
9. The article of claim 2 wherein said material incompatible with
polyethylene is ethylene vinyl alcohol copolymer.
10. The article of claim 2 wherein said regrind is trim or scrap
material from an article comprising (A) a layer comprising
polyethylene; (B) a layer comprising a material incompatible with
polyethylene; (C) regrind and at least one material selected from
low density metallocene polyethylene.
11. The article of claim 2 wherein said at least one material
selected from low density metallocene polyethylene is a plastomer
present in layer (C) in the amount of about 3 wt. % to about 20 wt.
%, based on the weight of said layer (C).
12. The article of claim 2 wherein said at least one material
selected from low density metallocene polyethylene is a plastomer
present in layer (C) in the amount of about 3 wt. % to about 15 wt.
%, based on the weight of said layer (C).
13. The article of claim 2 wherein said at least one material
selected from low density metallocene polyethylene is present in
layer (C) in an amount sufficient to impart increased impact
strength in said article, as measured by Gardener Impact Test at
-40.degree. C., relative to said layer without said at least one
material.
14. The article of claim 2 wherein layer (C) further comprises a
compatibilizer selected from at least one anhydride grafted
polyethylene.
15. The article of claim 2 further having an additional layer (D)
comprising polyethylene, which may be the same as or different from
layer (A).
16. The article of claim 15 wherein said article layered in the
order of A/B/C/D.
17. The article of claim 16 wherein at least one of layers (A) and
(D) comprises HDPE.
18. The article of claim 16 further comprising at least one
adhesive layer between layers (A) and (B) or between layers (B) and
(C), or both.
19. The article of claim 2 wherein layer (C) comprises greater than
about 40 wt. % of the weight of the entire article.
20. The article of claim 2 wherein layer (C) comprises at least
about 45 wt. % of the weight of the entire article.
21. The article of claim 2 wherein layer (C) comprises at least
about 50 wt. % of the weight of the entire article.
22. The article of claim 2 formed by a process comprising
thermoforming.
23. The article of claim 2 formed by a process comprising blow
molding.
24. The article of claim 18 formed by a process comprising
thermoforming.
25. The article of claim 2 wherein said article is a film or
article shaped by thermoforming.
26. A barrier layer fiel tank according to claim 24.
27. A barrier layer fuel tank according to claim 24 further
comprising gasoline.
28. An automobile comprising the barrier layer fuel tank according
to claim 26.
29. In a process of making an article including a step of forming a
layer comprising regrind, the improvement comprising adding at
least one low density polyethylene to said regrind and forming said
layer.
30. The process of claim 29, wherein said at least one low density
polyethylene is added in an amount sufficient to increase at least
one of the following characteristics of said article: (a) increase
the impact strength of said article, as measured by the Gardener
Impact Test at either room temperature or at -40.degree. C.; and
(b) increasing the amount of regrind in said article on a wt. %
basis.
31. The process of claim 29, wherein said regrind further comprises
a material incompatible with polyethylene.
32. A process comprising thermoforming an article comprising: A
layer comprising regrind from said process and at least one low
density metallocene polyethylene in an amount sufficient to
increase at least one of the following characteristics of said
article: (i) increase the impact strength of said article, as
measured by the Gardner Impact Test at either room temperature or
at -40.degree. C.; and (ii) increasing the amount of said regrind
in said article on a wt. % basis: And at least one layer selected
from (a) a layer comprising virgin polyethylene; and (b) a layer
comprising a material incompatible with polyethylene.
33. In a thermoforming process comprising making an article and
producing regrind, said article including: (A) a layer comprising
polyethylene; (B) a layer comprising a material incompatible with
polyethylene; and (C) a layer comprising regrind; the improvement
comprising adding at least one material selected from low density
metallocene polyethylenes to said layer comprising regrind; and
thermoforming said article.
34. The thermoforming process of claim 33 further comprising
removing trim from said article and recycling said trim as regrind
in layer (C) in said process.
35. The thermoforming process of claim 33 wherein said process
generates trim that is substantially entirely reused in said
process.
36. An article made by a process, said article comprising a layer
(A) comprising polyethylene, a layer (B) comprising a material
incompatible with polyethylene; and a layer (C) comprising regrind
from said process and at least one material selected form low
density metallocene polyethylenes, wherein said layer (C) comprises
greater than about 70 wt. % of the weight of the entire
article.
37. The article of claim 36 wherein said layer (C) comprises
greater than about 45 wt. % of the weight of the entire
article.
38. The article of claim 37 wherein said layer (C) comprises
greater than about 50 wt. % of the weight of the entire
article.
39. An article comprising a layer (A) comprising polyethylene, a
layer (B) comprising a material incompatible with polyethylene, and
a layer (C) of HDPE-containing regrind and a low density
metallocene polyethylene wherein said layer (C) comprises greater
than about 40 wt. % of the weight of said article.
Description
FIELD OF THE INVENTION
[0001] The invention relates to the addition of low density
metallocene polyethylene to regrind material in order to improve
impact strength of articles made using the regrind material.
BACKGROUND OF THE INVENTION
[0002] Many diverse structures are made of layers that are not
compatible when the layers are ground up and used in a regrind
layer. For instance, barrier fuel tanks for automobiles typically
include at least one layer comprising virgin HDPE, a barrier layer
comprising EVOH, polyamide (e.g., nylon), and the like, a layer
comprising regrind material, and several adhesive or tie layers to
bind the other layers. See, for instance, U.S. Application No.
2004/0071904.
[0003] A large amount of trim material is typically generated when
producing barrier fuel tanks by blow molding or thermoforming
methods. In order to make such processes more economical the trim
is reused in the process in the regrind layer. However, as the
regrind layer has poor impact strength, the amount of regrind that
can be used in the final structure is limited.
[0004] In current commercial operations, only about 35 wt. %
regrind (based on the weight of the entire automotive fuel tank)
can be incorporated into a new tank if the tank is to possess
certain desirable characteristics, such as passing the cold drop
(-40.degree. C.) test. The trim in current blow molding or
thermoforming operations can run as high as 60 wt. % of the weight
of the fuel tank, and thus there is the problem of an excess of
trim, which must then be sold as scrap.
[0005] The poor mechanical strength of regrind relative to the
polyethylene layer has been addressed in the prior art by various
methods, e.g., rearranging the order of layers (see, for instance,
paragraph [0148] of U.S. Patent Application 2002/0176955A1) or
providing a new adhesive material (see, for instance, U.S. Patent
Application 2003/0175538). As multilayer structures comprise more
and more diverse materials (see, for instance, EP 1108586, teaching
an automotive fuel tank having a second barrier layer of amorphous
carbon), the problem of the disposition of trim and other scrap
material grows. It would be beneficial if a higher amount of trim
could be used in the process that generates the trim, without
detracting from the important properties of the final product.
[0006] U.S. Pat. No. 6,223,945 discloses a bottle resistant to
stress crack comprising a multilayer resin structure having an
inner layer including a metallocene polyethylene, an optional
middle layer comprising post-consumer recycled resin (PCR), such as
HDPE bottle scrap or LLDPE recycled pallet stretch film, and an
outer layer comprising a higher density material.
[0007] U.S. Patent Application No. 2002/0086174 teaches multilayer
film structures having improved seal and tear properties having a
layer comprising regrind and a polyethylene having a density of
from about 0.93 g/cc to about 0.97 g/cc.
[0008] WO 03/000790 A1 teaches the use of VLDPE or LLDPE
polyethylene as impact modifiers for polypropylene.
[0009] EP 0622183 describes a multilayer film having a layer
comprising recycled material and a primer comprising an anhydride
modified polyolefin or copolymer.
[0010] Additional related references include U.S. Pat. Nos.
6,068,933; and 6,670,007; U.S. Application Nos. 2002/0051891, and
2003/0198768, Canadian Patent Application No. 2,122,283, and WO
98029245 A2.
[0011] The present inventors have surprisingly discovered that
addition of low density metallocene polyethylenes to regrind allows
an increase the amount of regrind that can be used in a useful
article, such as a multilayer structure comprising a regrind
layer.
SUMMARY OF THE INVENTION
[0012] The invention is directed to the use of low density
metallocene polyethylenes in regrind material.
[0013] In an embodiment, the addition of the low density
metallocene polyethylenes increases at least one of the properties
of melt strength of the material, or the impact strength the
article made therefrom, relative to the material or article,
respectively, without the addition of the low density metallocene
polyethylene.
[0014] In an embodiment the regrind having added thereto low
density metallocene polyethylene is used in a multilayer structure,
such as a multilayer film or sheet or a relatively large and
complex article such as a tank for holding fuel or other liquids or
gases, e.g., a barrier fuel tank. In a preferred embodiment the
structure is a thermoformed article. In another preferred
embodiment, the structure is a blow molded article.
[0015] It is an object of the present invention to provide a method
of increasing the amount of scrap material, particularly regrind,
in useful articles, particularly in useful articles already
utilizing scrap and more particularly regrind.
[0016] It is a further object of the invention to provide
scrap-containing articles having increased strength
characteristics, particularly impact strength.
[0017] These and other embodiments, objects, features, and
advantages will become apparent as reference is made to the
following detailed description, preferred embodiments, examples,
and appended claims.
DETAILED DESCRIPTION
[0018] According to the invention, at least one low density
metallocene polyethylene is added to regrind material.
[0019] Various types of polyethylenes are known in the art. For the
purposes of the present invention, the following descriptions of
polyethylenes apply. Low density polyethylene ("LDPE") can be
prepared at high pressure using free radical initiators and
typically has a density in the range of 0.916-0.940 g/cm.sup.3.
LDPE is also known as "branched" or "heterogeneously branched"
polyethylene because of the relatively large number of long chain
branches extending from the main polymer backbone. Polyethylene in
the same density range, i.e., 0.916 to 0.940 g/cm.sup.3, which is
linear and does not contain large quantities of long chain
branching is also known; this "linear low density polyethylene"
("LLDPE") can be produced with conventional Ziegler-Natta catalysts
or with single site catalysts, such as metallocene catalysts,
discussed further below. Relatively higher density LDPE or LLDPE,
typically in the range of 0.928 to 0.940 g/cm.sup.3 are sometimes
referred to as medium density polyethylene ("MDPE") or Linear
Medium Density Polyethylene (LMDPE), respectively. Polyethylenes
having still greater density are the high density polyethylenes
("HDPEs"), i.e., polyethylenes having densities greater than 0.940
g/cm.sup.3, and are generally prepared with Ziegler-Natta
catalysts, chrome catalysts or even single site catalysts such as
metallocene catalysts. Very low density polyethylene ("VLDPE") is
also known. VLDPEs can be produced by a number of different
processes yielding polymers with different properties, but can be
generally described as polyethylenes having a density less than
0.916 g/cm.sup.3, typically 0.890 to 0.915 g/cm.sup.3 or 0.900 to
0.915 g/cm.sup.3. VLDPEs produced using metallocene or other
single-site catalysts, as discussed further below, are referred to
as a type of plastomer. Plastomers having a density as low as 0.860
g/cm.sup.3 are commercially available. LLDPE and VLDPE produced
using metallocene catalysts which are useful in the present
invention are referred to herein as mLLDPE and mVLDPE,
respectively.
[0020] The present invention is directed to adding at least one low
density metallocene polyethylene, wherein the term "low density"
means a metallocene LLDPE having a density of about 0.916 g/cc to
about 0.940 g/cc or metallocene VLDPE having a density below 0.916
g/cc, preferably a density from about 0.860 g/cc to about 0.915
g/cc. In an embodiment, the low density metallocene polyethylene
will have a density of from about 0.860 g/cc to about 0.905 g/cc.
In another embodiment, the low density metallocene polyethylene
will have a density of from about 0.860 g/cc to less than 0.890
g/cc. Densities as used; herein are measured using ASTM D-1505.
[0021] Polyethylene generally may also be characterized as
homopolymers or copolymers of ethylene. Polymers having more than
two types of monomers, such as terpolymers, are also included
within the term "copolymer" as used herein.
[0022] The comonomers that are useful in the present invention
include alpha-olefins, such as C.sub.3-C.sub.20 alpha-olefin and
preferably C.sub.3-C.sub.12 alpha-olefins. The alpha-olefin
comonomer can be linear or branched, and two or more comonomers can
be used, if desired. Examples of suitable comonomers include linear
C.sub.3-C.sub.12 alpha-olefins, and alpha-olefins having one or
more C.sub.1-C.sub.3 alkyl branches, or an aryl group. Specific
examples include propylene; 3-methyl-1-butene;
3,3dimethyl-1-butene; 1-pentene; 1-butene; 1-pentene with one or
more methyl, ethyl or propyl substituents; 1-hexene; 1-hexene with
one or more methyl, ethyl or propyl substituents; 1-heptene with
one or more methyl, ethyl or propyl substituents; 1-decene;
1-dodecene; 1-octene with one or more methyl, ethyl or propyl
substituents; 1-nonene with one or more methyl, ethyl or propyl
substituents; ethyl, methyl or dimethyl-substituted 1-decene;
1-dodecene; and styrene. It should be appreciated that the list of
comonomers above is merely exemplary, and is not intended to be
limiting.
[0023] A "metallocene polyethylene" as used herein means a
polyethylene produced by a metallocene catalyst. As used herein,
the term "metallocene catalyst" is defined to be at least one
metallocene catalyst component containing one or more substituted
or unsubstituted cyclopentadienyl moiety (Cp) in combination with a
Group 4, 5, or 6 transition metal (M).
[0024] The metallocene catalyst precursors generally require
activation with a suitable co-catalyst, or activator, in order to
yield an "active metallocene catalyst", i.e., an organometallic
complex with a vacant coordination site that can coordinate,
insert, and polymerize olefins. The active catalyst systems
generally includes not only the metallocene complex, but also an
activator, such as an alumoxane or a derivative thereof (preferably
MAO), an ionizing activator, a Lewis acid, or a combination
thereof. Alkylalumoxanes are additionally suitable as catalyst
activators The catalyst system is preferably supported or a
carrier, typically an inorganic oxide or chloride or a resinous
material such as polyethylene.
[0025] The prior art is replete with examples of metallocene
catalysts/systems for producing polyethylene. Non-limiting examples
of metallocene catalysts and catalyst systems useful in practicing
the present invention include WO 96/11961; WO 96/11960; U.S. Pat.
Nos. 4,808,561; 5,017,714; 5,055,438; 5,064,802; 5,124,418;
5,153,157; 5,324,800; more recent examples are U.S. Pat. Nos.
6,380,122; and 6,376,410; and WO01/98409, and references cited
therein.
[0026] Included within the definition of the "metallocene
polyethylene" useful in the present invention are polyethylene
resins having a low polydispersity as described, for instance, in
U.S. Pat. No. 6,492,010, that is, a polydispersity produced by a
catalyst variously described as "single site", "constrained
geometry", or the aforementioned metallocene catalyst, catalysts
per se well known in the prior art.
[0027] Metallocene or low polydispersity resins useful in the
present invention are available from, among others, Dow Chemical
Company and Exxon Chemical Company who are producers of single site
or constrained geometry catalyzed polyethylenes. These resins are
commercially available as the ENHANCED POLYETHYLENE.TM., ELITE.TM.,
AFFINITY.TM., EXXACT.TM., and EXCEED.TM. polyethylene resins.
TAFMER.TM. resins, available from Mitsui Chemical Company and also
having low polydispersity, and having a density within the
aforementioned range for LLDPE and VLDPEs, are also useful in
present invention, and are included within the definition of the
term "metallocene polyethylene" for the purposes of the present
invention.
[0028] Also useful in the present invention and included within the
definition of metallocene polyethylenes useful in the present
invention are bimodal resins produced by catalysts having as at
least one component a metallocene polyethylene. Particularly
preferred examples are bimodal resins having as a component a resin
produced using a single site, constrained geometry, or metallocene
catalyst and having a density falling within the density range for
LLDPE and VLDPE as previously described. Bimodal resins are per se
well known in the art.
[0029] Accordingly, the low density metallocene polyethylene may be
selected from metallocene LLDPE (mLLDPE), metallocene VLDPE
(mVLDPE), or a mixture thereof. In an embodiment the low density
metallocene polyethylene is produced using a metallocene catalyst,
a single site catalyst, a constrained geometry catalyst, or it
maybe a low polydispersity, low density polyethylene resin, or it
may be a mixture of more than one of the aforementioned low density
metallocene polyethylenes.
[0030] In the case where the metallocene polyethylene is a
polyethylene copolymer, the preferred alpha olefin comonomer
content is below about 30 weight percent, preferably below about 20
weight percent, and more preferably from about 1 to about 15 weight
percent. Preferred comonomers include propylene, 1-butene,
1-pentene, 1-hexene, 3-methyl-1-pentene, 4-methyl-1-pentene,
1-octene, 1-decene, and 1-dodecene.
[0031] In an embodiment, the low density metallocene polyethylene
is a low polydispersity polyethylene resins, preferably having a
number average molecular weight in the range of from about 20,000
to about 500,000, more preferably from about 50,000 to about
200,000. The molecular weight maybe determined by commonly used
techniques such as size exclusion chromatography or gel permeation
chromatography. As is known in the art, however, molecular weight
is typically not an important characteristic by which metallocene
polyethylenes are described, but may vary depending on the process
in which it is to be used (e.g., thermoforming technique) and the
characteristics desired in the end product.
[0032] In an embodiment, the polyethylene resin according to the
present invention will have a molecular weight distribution, or
polydispersity, (Mw/Mn, or MWD) within the range of about 1 to
about 4, preferably about 1.5 to about 4, more preferably about 2
to about 4, and even more preferably from about 2 to about 3, as
determined by gel permeation chromatography (GPC) using a DRI
refraction index detector, i.e., a Waters 150C GPC instrument with
DRI detectors. Such products are well known in the art per se and
are discussed, for instance, in U.S. Pat. Nos. 5,907,942;
5,907,943; 5,902,684; 5,752,362; 5,814,399; and 5,749,202.
[0033] In an embodiment, the low polydispersity polymers this
produced generally have a crystalline content in excess of at least
10 weight percent, generally in excess of at least 15 weight
percent.
[0034] In a more preferred embodiment, useful mLLDPE and mVLDPE
resins suitable for the present invention include those sold under
the Exact or Exceed trademarks, both available from ExxonMobil
Chemical Company, Houston, Tex., USA. Particularly preferred is
Exact.TM. 8021 polyethylene, a 1.0 MI.sub.2, 0.882 density
plastomer, Exact.TM. 0201 polyethylene, a 1.1 MI.sub.2, 0.902
density resin, and Exceed.TM. 1012 polyethylene a 1.0 MI.sub.2,
0.912 density resin available from ExxonMobil Chemical Company.
[0035] The amount of the at least one low density metallocene
polyethylene added to the regrind will be, in an embodiment, an
amount sufficient to impart increased impact strength in the
desired finished article, e.g., barrier fuel tank, as measured by a
Gardener Impact Test (ASTM D-5420), which may be measured at, for
instance, room temperature or a cold temperature test at
-40.degree. C. In another embodiment, the amount of low density
metallocene resin added to the regrind layer is about 3 wt. % to
about 20 wt. %, or 3 wt. % to about 15 wt. %, based on the weight
of the regrind layer.
[0036] As used herein, the term "regrind" means the diverse
materials, including trim and non-compliant articles, which are
typically ground up by conventional size reduction techniques and
reused or otherwise recycled (e.g., in the process from which the
regrind is generated or into some other process). In an embodiment
the regrind is trim or scrap from a thermoforming or other
technique involving molding, particularly blow molding. In an
embodiment, the regrind has added thereto the low density
metallocene polyethylene resin according to the invention and then
is used back in the process generating the trim. In an embodiment
the regrind is ground to a preselected mesh size. Although the term
"regrind" implies grinding of the material, it will be recognized
by one of ordinary skill in the art in possession of the present
disclosure that the scrap material can simply be thrown into a
hopper and melted with the low density metallocene polyethylene
according to the invention. The low density metallocene
polyethylene resin may be added to the regrind in-line or it may be
separately mixed with regrind, extruded into pellets, and then
added to the thermoforming or other forming operation making an
article utilizing a regrind layer. In an even more preferred
embodiment the trim is from a thermoforming process, yet even more
preferably such a process making automotive barrier fuel tanks, and
the regrind from this trim is used back in the thermoforming
process in-line to make an automotive barrier fuel tank. The
regrind may also have added thereto known compatibilizers such as
anhydride grafted polyethylene, e.g., maleic anhydride grafted
polyethylene.
[0037] The benefits of the present invention are especially seen in
the case where regrind contains material incompatible with
polyethylene but it will be recognized by one of ordinary skill in
the art that benefits may also be seen with material that consists
essentially of one or more polyethylenes. The benefits may also be
seen in a single layer film or sheet but more particularly in a
multilayer film or sheet, and even more particularly in complex
articles, it being understood that the term "article" as used
herein also includes a single layer of film.
[0038] Material incompatible with polyethylene means in its most
general sense material that is more polar than homopolymers of
ethylene or copolymers of ethylene and an alpha olefin comonomer,
and also includes material that is immiscible with the polyethylene
when blended and forms a second phase within the polyethylene
matrix or wherein polyethylene forms a second phase within the
matrix of said incompatible material. In an embodiment, such
materials will be selected from polypropylene, functionalized
polyolefins, polyketones, polyesters, polyamides, ethylene vinyl
acetates (EVA), ethylene vinyl alcohols (EVOH), and styrenic
resins. Functonalized polyolefins means polyolefins having groups
containing polar molar molecules, particularly nitrogen,
phosphorus, oxygen, sulfur, and halogens. Preferred styrenic resins
are polystyrene and ABS. In a preferred embodiment, the materials
incompatible with polyethylene are those resins described as
barrier layer materials in the aforementioned U.S. 2002/0051891 A1,
U.S. 2002/0176955 A1, U.S. 2003/0175538 A1, U.S. 2003/0198768 A1,
and WO 98029245 A2. In a preferred embodiment, the material
incompatible with polyethylene is selected from EVOH, polyamides,
and mixtures thereof. A particularly advantageous effect is
observed when the material incompatible with polyethylene is
EVOH.
[0039] In an embodiment of a multilayer structure according to the
present invention, in addition to the regrind layer and layer
having material incompatible with polyethylene, there is a layer
comprised of a polyethylene which is preferably HDPE. In a
preferred embodiment this polyethylene layer is virgin
polyethylene, meaning it has not previously been used in an
article. In a more preferable embodiment, this layer comprises
virgin HDPE, which may be a homopolymer or copolymer of HDPE. In an
embodiment, the layer comprises an HDPE copolymer of ethylene and a
C.sub.3-C.sub.12 alpha olefin. In another embodiment, the layer
comprised of polyethylene is an alloy of polyethylene with a
barrier material, such as Orgalloy.TM. resin, available from
Atofina. In another embodiment the layer comprises a blend of
polyethylenes.
[0040] In one embodiment, the HDPE polymer may have a melt index
from 0.01 to 45 g/10 min, as measured in accordance with ASTM-1238
condition E. In another embodiment, the HDPE has a density of from
about greater than 0.940 g/cc to about 0.965 g/cc and an HLMI of
from about 3.0 to about 40.0 g/10 min (ASTM D-1238-65T, Condition
F). The HDPE polymer may be produced using any conventional
polymerization process, such as a solution, a slurry, or a
gas-phase process, and a suitable catalyst, such as a chrome
catalyst, a Ziegler-Natta catalyst or a metallocene catalyst. It is
preferred that the HDPEs used in the blends according to the
present invention be produced using Zeigler-Natta catalysts.
[0041] Examples of suitable HDPE useful in the present invention
include HDPEs available from ExxonMobil Chemical Co., Houston,
Tex., under the HD, HDA, HMA, HRA, HRP, HDZ or HYA series or under
the trademark PAXON. Examples of HDPE include HYA800, produced in
the gas phase, and HDZ222, produced by the stirred slurry process
and BA46-055, produced in the slurry loop process, the latter also
available from ExxonMobil Chemical Company. Blends of two or more
HDPE polymers and one or more HDPE polymers with one or more
non-HDPE polymers are also contemplated.
[0042] Non-HDPE polymers include any of the other polyethylene
resins set forth herein (e.g., LMDPE) or it maybe some other
polyolefin such as polypropylene. In an embodiment, this layer
excludes polypropylene. In an embodiment, the HDPE layer consists
essentially of virgin HDPE. In another embodiment, the HDPE layer
may be a polyethylene alloy such as Orgalloy.TM. resin, as
previously mentioned.
[0043] The layer comprising polyethylene may contain a major
portion (meaning 50 wt. % or more, based on the weight of this
layer) of a resin that is not an HDPE, e.g., one of the other
polyethylenes recited herein, such as LMDPE, LLDPE, or VLDPE, or it
may contain a minor portion of such resins. It is preferred,
however, that in the case of a thermoformed article, that this
polyethylene layer consist essentially of polyethylene and
preferred that it does not contain regrind.
[0044] Additional optional layers include adhesive or tie layers
between one or more of the aforementioned layers and also
additional layers having different functions, such as those set
forth in the prior art described herein, e.g., more than one
barrier layer having the same or different properties, more than
one regrind layer having the same or different properties, more
than one polyethylene layer having the same or different
properties, and the like, as would be appreciated by one of
ordinary skill in the art in possession of the present
disclosure.
[0045] The ordering of layers will depend on the desired properties
but typically will include: (A) a layer comprising polyethylene,
preferably at least one HDPE; (B) a layer comprising a material
incompatible with polyethylene; and (C) a layer comprising regrind
and at least one material selected from low density metallocene
polyethylene according to the present invention. In a preferred
embodiment the order will be A/B/C, and typically adhesive layers
will be present between each of these layers. It will be understood
by one of skill in the art that the conventional description
"A/B/C" is shorthand for a layer comprising (A), followed by a
layer comprising (B), followed by a layer comprising (C), with the
option(s) of additional layers before, after, or between each of
the specified layers, or a combination of any two of said options
or all three options as contemplated embodiments. In another
preferred embodiment there will be a second polyethylene layer (D),
which may be the same or different than (A), in the order A/B/C/D.
Whether (A) and (D) are the same or different, it is preferred that
both comprise at least one material selected from HDPE. An adhesive
layer may be present between C and D, or there may be no adhesive
layer between C and D. In an embodiment, wherein a container is
thermoformed comprising layers A/B/C/D and wherein layer D is an
inner layer in contact with a liquid or gas, layers A and D, both
comprising HDPE, may be the same or different, and in a preferred
embodiment layer A consists essentially of virgin HDPE and layer D
consists essentially of Orgalloy.TM. resin.
[0046] It is a particular advantage of the present invention that
the addition of the at least one low density metallocene
polyethylene increases the amount of regrind that can be used in
the final structure. In a preferred embodiment the regrind layer
comprises greater than 40 wt. %, or at least about 45 wt. %, or at
least about 50 wt. % of the final structure. In embodiment, which
may be a film or sheet or other article shaped by thermoforming or
other molding technique, comprising the previously recited
structure A/B/C or A/B/C/D, with or without various adhesive
layers, the layer (C) comprising regrind and the low density
metallocene polyethylene according to the present invention
comprises greater than 40 wt. %, or at least 45 wt. %, or at least
50 wt. %, of the entire structure.
[0047] An article comprising the regrind and low density
polyethylene according to the present invention may be a single
layer or multilayer film or sheet, or a more complex article such
as a container, for instance a barrier fuel tank, and the like, and
it may be formed by any method such as, without limitation,
coextrusion, thermoforming, or other molding technique,
particularly blow molding. Preferred articles include multilayer
films and sheets which may be subsequently formed into some other
useful article, containers for liquids or gases, particularly a
fuel, and more particularly gasoline, and also the article
comprising such a container or film, e.g., an automobile having a
barrier fuel tank.
[0048] Having thus generally described the present invention, the
following specific examples are provided as representative examples
and are not intended to limit the invention.
[0049] Four low density metallocene polyethylenes were evaluated at
levels of 5 and 10% in regrind materials from a typical commercial
thermoforming process manufacturing a barrier fuel tank having the
structure A/B/C/D, wherein layers A and D consist of virgin HDPE,
layer B is a barrier layer consisting of EVOH, and layer C is the
regrind layer comprising trim from the process and having a total
EVOH content of approximately 9 wt. %. There is an adhesive layer
between layers A and B, and also between layers B and C, the
adhesive being Admer.TM. from Mitsui Chemical, a maleated linear
low density polyethylene. Samples of trim regrind were reduced to a
particle size sufficient to allow operation of the twin screw
extruder, compounded with low density metallocene polyethylene
according to the present invention (except Example 1) and
pelletized on the 30 mm ZSK twin screw extruder under standard
operating conditions resulting in a melt temperature of 450.degree.
F. (about 232.degree. C.). The pellets were then pressed into
plaques and tested for impact strength. In Examples 1-5, impact
data was measured according to Gardener Impact Test at room
temperature (ASTM D-5420). Unmodified regrind was also run in the
same manner, without compounding, to provide a reference point
(Example 1). In Example 6, a dynamic impact test is performed using
ASTM D-3763-98 at -40.degree. C. The Gardener Impact Test is a
falling dart test, where a dart is dropped from different heights;
the height it takes to break the sample is then converted into
energy. In the dynamic impact test, the amount of energy it takes
to drive a dart through the specimen is measured.
EXAMPLE 1
[0050] Regrind without the low density metallocene polyethylene
according to the invention is treated as just described. The
Gardener Impact strength of the resulting material was measured
according to ASTM D-5420 at 350 in-lb (39.55 Joules).
EXAMPLE 2
[0051] Example 1 was repeated except that 5 wt. % of Exact.TM. 8201
polyethylene is added in-line to the regrind, based on the weight
of the regrind layer. The Gardener Impact strength of the resulting
material was measured at 427 in-lb (48.25 Joules).
EXAMPLE 3
[0052] Example 1 was repeated except that 10 wt. %, of Exact.TM.
8201 polyethylene is added in-line. The resultant material
exhibited a Gardener Impact Strength of 480 in-lb (54.24
Joules).
EXAMPLE 4
[0053] Example 1 was repeated except that 5 wt. % of Exceed.TM.
1012 polyethylene is added in-line. The Gardener Impact strength of
the resulting material was measured to be 403 in-lb (45.54
Joules).
EXAMPLE 5
[0054] Example 1 is repeated except that 10 wt. % of Exceed.TM.
1012 polyethylene is added in-line. The Gardener Impact Strength of
the resulting material was measured to be 445 in-lb (50.29
Joules).
EXAMPLE 6
[0055] Additional plaques using regrind and the low density
metallocene polyethylenes used in Examples 2-5 were tested using a
dynamic impact test or Dyna-tup test according to ASTM D-3763-98 at
-40.degree. C. While the dynamic impact strength for each of the
samples using the Exceed.TM. 1012 and Exact.TM. 8201 polyethylenes
showed an improvement over the bare regrind, the sample using 10
wt. % Exact.TM. 8201 was superior to the other samples, having an
Gardener Impact strength of approximately 26 Joules. For
comparison, using a plaque consisting of virgin HDPE (BA 46-055
HDPE available from ExxonMobil Chemical Company) and tested in the
same manner at -40.degree. C. yielded a measurement of
approximately 24 Joules.
[0056] The present invention is particularly useful in
thermoforming processes and other processes involving molding,
particularly blow molding, wherein regrind material is used or more
generally wherein material comprising plastics is recycled. It is
useful in process making articles such as mono- or multilayer webs,
mono- or multilayer films and sheets, and combinations of webs,
films and sheets, also hollow bodies, for example tubes, bottles
and other containers, such as gas tanks, and other useful articles
such as automobile bumpers, and the like.
[0057] Having described the invention with reference to a general
description, a detailed description, and specific examples, the
following is yet a further description of some preferred
embodiments of the present invention: (I) an article comprising
regrind and at least one material selected from low density
polyethylenes; and also one or more of the following more preferred
embodiments: said article comprising (A) a layer comprising
polyethylene; (B) a layer comprising a material incompatible with
polyethylene; and (C) a layer comprising regrind and at least one
material selected from low density metallocene polyethylenes,
particularly wherein said polyethylene in layer (A) is selected
from HDPE homopolymer, HDPE copolymer of ethylene and a C3-C12
alpha olefin, and mixtures thereof; wherein any of the
aforementioned articles has at least one layer comprising an alloy
or blend of polyethylene; and/or wherein any of the aforementioned
articles further comprises at least one adhesive layer, preferably
wherein said adhesive layer comprises a maleated LLDPE; wherein
layer (A) in any of the aforementioned articles comprises, consists
essentially of, or consists of an HDPE having a density of from
greater than about 0.940 g/cc to about 0.965 g/cc according to ASTM
D-4883 and an HLMI of from about 3.0 to about 40.0 according to
ASTM D-1238-65T, Condition F; any of the aforementioned articles
having a layer comprising material incompatible with polyethylene,
wherein said material incompatible with polyethylene is a material
comprising a resin selected from ethylene vinyl alcohol, polyamide,
polyketone, ethylene vinyl acetate, polyester, and mixtures
thereof, particularly wherein said material incompatible with
polyethylene is a material comprising a resin selected from
ethylene vinyl alcohol, polyamide, and mixtures thereof, even more
preferably wherein said material incompatible with polyethylene is
ethylene vinyl alcohol; also preferably wherein any of the
aforementioned articles the regrind is trim material from an
article comprising (A) a layer comprising polyethylene; (B) a layer
comprising a material incompatible with polyethylene; (C) regrind
and at least one material selected from low density metallocene
polyethylene or in another embodiment is trim material comprising
polyethylene (preferably HDPE and more preferably HDPE
homopolymer), a material incompatible with polyethylene (such as a
barrier material as recited herein, particularly EVOH), and a
mixture of regrind and at least one low density metallocene
polyethylene; and also any of the aforementioned articles having a
layer (C) as described herein wherein said at least one material
selected from low density metallocene polyethylene plastomer is
present in layer (C) in the amount of about 3 wt. % to about 20 wt.
%, based on the weight of said layer (C), more preferably wherein
said at least one material selected from low density metallocene
polyethylene plastomer is present in layer (C) in the amount of
about 3 wt. % to about 15 wt. %, based on the weight of said layer
(C); or any of the aforementioned articles wherein said at least
one material selected from low density metallocene polyethylene is
present in layer (C) in an amount sufficient to impart increased
impact strength in said article, as measured by Gardener Impact
Test at -40.degree. C., or increase the melt strength of said layer
or said article, as measure by any known method of measuring melt
strength, or increase the amount of recycled material in said
article, relative to said layer without said at least one material;
or any of the aforementioned articles having a layer (C) as set
forth herein wherein layer (C) further comprises a compatibilizer
selected from at least one anhydride grafted polyethylene; or any
of the aforementioned articles having a layer (A) as set forth
herein, further having a layer (D) comprising polyethylene, which
may be the same or different from layer (A), particularly such an
article having layers (A) through (D) as set forth herein, said
article layered in the order of A/B/C/D, more preferably wherein at
least one of layers (A) and (D) comprises HDPE, with or without
adhesive layers between one or more of the layers, particularly
comprising at least one adhesive layer between layer (A) and (B),
and between layer (B) and (C); and any of the aforementioned
articles having a layer (C) as set forth herein, wherein layer (C)
comprises greater than about 40 wt. % of the weight of the entire
article, more preferably wherein layer (C) comprises at least about
45 wt. % of the weight of the entire article, still more preferably
wherein layer (C) comprises at least about 50 wt. % of the weight
of the entire article; and any of the aforementioned formed by or
obtainable by a process comprising thermoforming, any of the
aforementioned articles formed by or obtainable by a process
comprising blow molding. It will be recognized that the article may
be a simple single layered sheet or film, a multilayered film or
sheet, or a complex article, such as an automotive part, e.g., a
fuel tank or other container for solids, liquids or gases. It may
be the container per se or it may be the container and a solid,
liquid, or gas, e.g., it may be a barrier layer fuel tank with
gasoline. The invention also contemplates a useful machine
comprising said article, e.g., an automobile comprising the barrier
layer fuel tank with or without fuel; (II) a process of making an
article including a step of forming a layer comprising regrind, the
improvement comprising adding at least one low density polyethylene
to said regrind and forming said layer; particularly wherein said
at least one low density polyethylene is added in an amount
sufficient to increase at least one of the following
characteristics of said article: (a) increase the impact strength
of said article, as measured by the Gardener Impact Test at either
room temperature or at -40.degree. C.; and (b) increasing the
amount of regrind in said article on a wt. % basis, or wherein the
amount of at least one low density polyethylene is added in an
amount sufficient to increase the melt strength of said regrind;
preferably any of the aforementioned processes wherein said regrind
further comprises a material incompatible with polyethylene;
preferably any of the aforementioned processes further comprising a
step of thermoforming an article comprising said layer comprising
regrind and at least one layer selected from (a) a layer comprising
virgin polyolefin; and (b) a layer comprising a material
incompatible with polyethylene; (III) a thermoforming process
comprising making an article including: (A) a layer comprising
polyethylene; (B) a layer comprising a material incompatible with
polyethylene; and (C) a layer comprising regrind; the improvement
comprising adding at least one material selected from low density
metallocene polyethylenes to said layer comprising regrind and
thermoforming said article; preferably said process further
comprising removing trim from said article and recycling said trim
as regrind in layer (C) in said process; preferably any of the
aforementioned processes wherein said process generates trim that
is substantially entirely reused in said process; and (IV) a
container, preferably a barrier layer fuel tank, comprising regrind
layer said regrind layer comprising greater than 40 wt. %, or at
least about 45 wt. %, or at least about 50 wt. % of said container,
and having, in preferred embodiments, any one or more of the
features contemplated as preferred embodiments set forth in (I) of
this paragraph, or such a container (particularly a barrier layer
fuel tank) made by any of the processes set forth in (II) or (III)
of this paragraph.
[0058] While the illustrative embodiments of the invention have
been described with particularity, it will be understood that
various other modifications will be apparent to and can be readily
made by those skilled in the art without departing from the spirit
and scope of the invention. Accordingly, it is not intended that
the scope of the claims appended hereto be limited to the examples
and descriptions set forth herein but rather that the claims be
construed as encompassing all the features of patentable novelty
which reside in the present invention, including all features which
would be treated as equivalents thereof by those skilled in the art
to which the invention pertains. Many variations will suggest
themselves to those skilled in this art in light of the above
detailed description. All such obvious variations are within the
full intended scope of the appended claims.
[0059] Trade names used herein are indicated by a .TM. symbol or
.RTM. symbol, indicating that the names may be protected by certain
trademark rights, e.g., they may be registered trademarks in
various jurisdictions. All patents and patent applications, test
procedures (such as ASTM methods, UL methods, and the like), and
other documents cited herein are fully incorporated by reference to
the extent such disclosure is not inconsistent with this invention
and for all jurisdictions in which such incorporation is permitted.
When numerical lower limits and numerical upper limits are listed
herein, ranges from any lower limit to any upper limit are
contemplated.
* * * * *